Multi-scale analysis of the damage and contamination in abrasive water jet drilling of GLARE fibre metal laminates

Abstract

The goal of this study is to investigate the influence of Abrasive Water Jet (AWJ) parameters (standoff distance, water pressure and abrasive flow rate) on the machining quality (diameter, circularity, abrasive contamination, surface roughness and types of damage) during drilling of thick hybrid material viz. GLARE (Glass Laminate Aluminium Reinforced Epoxy) Fibre Metal Laminates (FML). The novelty of this work is the use of X-ray tomography and image post-processing for the quantification of abrasive contamination in function of the machining parameters. Moreover, the indicator called ‘power of erosion’ (E), depending on the AWJ drilling parameters chosen, has permitted to estimate a threshold below which no delamination is found. The results have shown that oversized holes (up to 6.2 mm in diameter) were produced under all cutting parameters regardless of their level. Increasing the standoff distance increased the hole size and cylindricity. The main types of damage consecutive AWJ drilling are in form of barrelling at plies level and delamination with embedded particles. For ‘power of erosion’ (E) values below 0.17, no delamination is found. As increasing this indicator further, delamination occurs in-between plies closer to the jet entry and more contamination is observed (up to 4 % of the total scanned surface). The surface roughness was found to be in a similar range to that reported in conventional drilling studies of GLARE (<6 μm), which suggests that AWJC could provide a similar machining performance suitable for aerospace applications.